The value of the PSA test to screen men for prostate cancer has long been debated, and a new study of 162,000 men may not resolve the issue.

The European study, reported Aug. 6 in The Lancet, finds that widespread use of prostate-specific antigen (PSA) blood tests does reduce deaths from the disease by about one-fifth.

However, due to lingering doubts about whether the benefits of PSA screening outweigh the risks, the study's authors still recommend against routine use of the test at this time.

"PSA screening delivers a substantial reduction in prostate cancer deaths, similar or greater than that reported in screening for breast cancer," study lead author Fritz Schroder, of the Erasmus University Medical Center in the Netherlands, said in a journal news release.

"However, overdiagnosis occurs in roughly 40 percent of cases detected by screening resulting in a high risk of overtreatment and common side effects such as incontinence and impotence," he added.

In the context of prostate cancer, "overdiagnosis" means that some men may receive a diagnosis of prostate cancer from their PSA test, but the tumor may be so slow-growing that it might not pose a major threat to their health. However, the positive test result may still cause many patients to opt for treatments that entail side effects.

The new study included more than 162,000 men ages 50 to 74 in eight European countries. The men were randomly selected to have PSA screening every two or four years, or no PSA screening.

Compared to men who weren't screened, death rates among men in the screening group were 15 percent lower after nine years, 22 percent lower after 11 years, and 21 percent lower after 13 years, according to the study.

Schroder's team noted that not all men selected for screening went for the tests. After 13 years, those who were actually screened were 27 percent less likely to die of prostate cancer than those who were not screened.

The study also found that, 13 years into the study, 781 men needed to be invited for screening to prevent one prostate cancer death.

Based on the study findings, Schroder believes that the "time for population-based screening has not arrived. Further research is urgently needed on ways to reduce overdiagnosis preferably by avoiding unnecessary biopsy procedures, and reducing the very large number of men who must be screened, biopsied, and treated to help only a few patients."

Two experts in the United States agreed with Schroder's assessment.

The study "reinforces urologists' concern about overdiagnosis and overtreatment of prostate cancer using PSA screening alone," said Dr. Art Rastinehad, director of interventional urologic oncology at North Shore-LIJ's Arthur Smith Institute for Urology in New Hyde Park, N.Y.

But he added that evolving diagnostic technologies "may allay these understandable concerns. Indeed, The Lancet study authors proposed that new screening tools may hold the key to better selecting patients for biopsy and subsequent treatment."

Dr. Arul Chinnaiyan is professor of urology at the University of Michigan and director of the Michigan Center for Translational Pathology in Ann Arbor. He agreed with Rastinehad that the study "emphasizes the need for better diagnostic biomarkers or imaging technologies to detect aggressive forms of prostate cancer in a specific fashion."